function Dotline(option){
    this.opt = this.extend({
        dom:'J_dotLine',//画布id
        cw:1000,//画布宽
        ch:500,//画布高
        ds:100,//点的个数
        r:0.5,//圆点半径
        dis:100//触发连线的距离
    },option);
    this.c = document.getElementById(this.opt.dom);//canvas元素id
    this.ctx = this.c.getContext('2d');
    this.c.width = this.opt.cw;//canvas宽
    this.c.height = this.opt.ch;//canvas高
    this.dotSum = this.opt.ds;//点的数量
    this.radius = this.opt.r;//圆点的半径
    this.disMax = this.opt.dis*this.opt.dis;//点与点触发连线的间距		
    this.dots = [];
    //requestAnimationFrame控制canvas动画
    var RAF = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) {
                window.setTimeout(callback, 1000 / 60);
            };
    var _self = this;
    //增加鼠标效果
    var mousedot = {x:null,y:null,label:'mouse'};
    this.c.onmousemove = function(e){
        var e = e || window.event;
        mousedot.x = e.clientX - _self.c.offsetLeft-110;
        mousedot.y = e.clientY - _self.c.offsetTop-90;
    };
    this.c.onmouseout = function(e){
        mousedot.x = null;
        mousedot.y = null;
    }
    //控制动画
    this.animate = function(){
        _self.ctx.clearRect(0, 0, _self.c.width, _self.c.height);
        _self.drawLine([mousedot].concat(_self.dots));
        RAF(_self.animate);
    };
}
//合并配置项，es6直接使用obj.assign();
Dotline.prototype.extend = function(o,e){
    for(var key in e){
        if(e[key]){
            o[key]=e[key]
        }
    }
    return o;
};
//画点
Dotline.prototype.addDots = function(){
    var dot;
    for(var i=0; i<this.dotSum; i++){//参数
        dot = {
            x : Math.floor(Math.random()*this.c.width)-this.radius,
            y : Math.floor(Math.random()*this.c.height)-this.radius,
            ax : (Math.random() * 2 - 1) / 1.5,
            ay : (Math.random() * 2 - 1) / 1.5
        }
        this.dots.push(dot);
    }
};
//点运动
Dotline.prototype.move = function(dot){
    dot.x += dot.ax;
    dot.y += dot.ay;
    //点碰到边缘返回
    dot.ax *= (dot.x>(this.c.width-this.radius)||dot.x<this.radius)?-1:1;
    dot.ay *= (dot.y>(this.c.height-this.radius)||dot.y<this.radius)?-1:1;
    //绘制点
    this.ctx.beginPath();
    this.ctx.arc(dot.x, dot.y, this.radius, 0, Math.PI*2, true);
    this.ctx.stroke();
};
//点之间画线
Dotline.prototype.drawLine = function(dots){
    var nowDot;
    var _that = this;
    //自己的思路：遍历两次所有的点，比较点之间的距离，函数的触发放在animate里
    this.dots.forEach(function(dot){
        
        _that.move(dot);
        for(var j=0; j<dots.length; j++){
            nowDot = dots[j];
            if(nowDot===dot||nowDot.x===null||nowDot.y===null) continue;//continue跳出当前循环开始新的循环
            var dx = dot.x - nowDot.x,//别的点坐标减当前点坐标
                dy = dot.y - nowDot.y;
            var dc = dx*dx + dy*dy;
            if(Math.sqrt(dc)>Math.sqrt(_that.disMax)) continue;
            // 如果是鼠标，则让粒子向鼠标的位置移动
            if (nowDot.label && Math.sqrt(dc) >Math.sqrt(_that.disMax)/2) {
                dot.x -= dx * 0.02;
                dot.y -= dy * 0.02;
            }
            var ratio;
            ratio = (_that.disMax - dc) / _that.disMax;

            _that.ctx.beginPath();
            _that.ctx.lineWidth = ratio / 2;
              _that.ctx.strokeStyle = 'rgba(0,0,0,' + (ratio + 0.2) + ')';
            _that.ctx.moveTo(dot.x, dot.y);
            _that.ctx.lineTo(nowDot.x, nowDot.y);
            _that.ctx.stroke();//不描边看不出效果

            //dots.splice(dots.indexOf(dot), 1);
        }
    });
};
//开始动画
Dotline.prototype.start = function(){
    var _that = this;
    this.addDots();
    setTimeout(function() {
         _that.animate();
    }, 100);
}
//调用
window.onload = function(){
    var dotline = new Dotline({
        dom:'J_dotLine',//画布id
        cw:800,//画布宽
        ch:500,//画布高
        ds:50,//点的个数
        r:0.5,//圆点半径
        dis:80//触发连线的距离
    }).start();
}